Process for removing trace olefins from paraffin hydrocarbon containing streams



Oct. 25, 1966 J, VAN P 3,281,484

PROCESS FOR REMOVING TRACE OLEFINS FROM PARAFFIN HYDROCARBON CONTAINING STREAMS Filed 001;. 17, 1963 46 If F15 UBZIGIYO i (9 I (D (0 i 0") aazlolxo $1 I x I 1) m r) r0 7? o a r 0 MIX VAT l BOLVHHLVS -i Q INVENTOR. JOE VAN POOL N BY my ATTORNEYS United States Patent 3 281 484 PROCESS FOR REIVIOVING TRACE OLEFINS FROM PARAFFIN HYDROCARBON CON- TAINING STREAMS Joe Van Pool, Bartlesville, 0kla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed Oct. 17, 1963, Ser. No. 316,839 1 Claim. (Cl. 260-676) This invention relates to a process for the treatment of hydrocarbons. More particularly, this invention relates to a process for treating hydrocarbons so as to remove undesirable unsaturated contaminants therefrom.

In many petroleum refinery operations, the removal of olefins from hydrocarbon fractions is accomplished by treating the olefin-containing fraction with strong sulfuric acid. This method is commonly referred to as acid treating. This method is effective in reducing the olefin content of the hydrocarbon fraction in question and has been widely adopted by the industry, but the removal of olefins is not complete, and olefin contaminant remains in the hydrocarbon reaction.

In addition, in many other systems designed for the purification of hydrocarbon streams contaminated with an olefinic constituent, the purification process fails to remove essentially all of the contaminating materials, and thus the resulting product of the process is unsuitable for use as a chemical grade product.

By the present invention, the olefinic hydrocarbons are substantially completely removed from the hydrocarbon fraction.

Accordingly, it is an object of the present invention to provide a process for the production of hydrocarbons free of olefinic contaminants. Another object of this invention is to provide a method for the removal of contaminating olefin compounds from a hydrocarbon stream. A still further object of the invention is to provide a process for the production of chemical grade hydrocarbons.

Other objects, advantages and features of the invention will be readily apparent to those skilled in the art from the following description, the drawing and the appended claim.

In accordance with the invention, a method is pro- 'vided for treating hydrocarbon streams containing a contaminating amount of olefin compounds which comprises treating the stream with a potassium permanganate solution so as to oxidize the olefins therein to the corresponding alcohols, separating the thus formed alcohols from the system, and thereafter recovering the hydrocarbon free of olefinic bodies as a product of the process.

The process can best be described by reference to the accompanying drawing, which is a diagrammatic representation of the process of the invention. While the illustrated process is applied to the recovery of n-butane free of olefinic materials, it is not intended to limit the invention thereto, and other hydrocarbon streams or mixtures of hydrocarbons can be similarly treated in accordance with the invention.

Referring now to the drawing, 15,000 barrels/day of liquid n-butane derived from a conventional fractionating unit and containing about 350 ppm. of olefins (butylenes) is introduced into a saturator 11 via conduit 12 and pump 13. Water (e.g., steam condensate) is introduced through conduit 14 into an upper zone of saturator 11.

The feed to oxidizer 15 is preferably saturated with Water prior to treatment with the aqueous potassium permanganate solution in order that water is not removed from the solution by the hydrocarbon. Such pretreatment of the hydrocarbon with water prevents the re- "ice agent from becoming concentrated due to loss of water therefrom. Liquid level (interface) controller 24 serves to maintain the desired water liquid level within saturator 11. The hydrocarbon (now saturated with water) is then taken overhead and introduced into first stage oxidizer 15 via conduit 16.

Efiluent from first stage oxidizer 15 is removed overhead and introduced into second stage oxidizer 18 via conduit 17. Overhead from oxidizer 18 is passed to water wash column 20 via conduit 21. Water at a rate of about 50 barrels/day is passed into the wash column via conduit 22. The aqueous phase containing the oxidized olefins is removed via conduit 23 for disposal, recovery, or other desired subsequent handling.

Flow through conduit 23 is regulated by liquid level (interface) controller 25 and motor valve 26 responsive thereto. Overhead from wash column 20 comprising essentially olefin-free (5 ppm. olefin) n-butane liquid is removed at a rate of 15,000 barrels/day and passed via conduit 27 to storage or for other use as desired.

Within oxidizers 15 and 18 the water-saturated olefinscontaining liquid hydrocarbon mixture is contacted with an aqueous solution of potassium permanganate introduced by means of conduits 28 and 29. The interface level in the column is regulated by liquid level (interface) controllers 30 and 31. The aqueous potassium permanganate solution employed in oxidizers 15 and 18 is prepared by introducing 190 barrels/day water (e.g., steam condensate) through conduit 55 and 1800 to 2000 lbs/day of potassium permanganate into potassium permanganate mixing vat 31 by way of conduit 56. Steam to assist in the formation of the potassium permanganate solution can be added via conduit 32. The resulting solution is then removed via pump 33 and conduit 34 for introduction into the oxidizers. Recycle for complete solution of the potassium permanganate can be achieved when operating pump 33 by means of valve 35 and conduit 36. The concentration of the aqueous potassium permanganate solution can be about 2 to 5 weight percent potassium permanganate for most economical operations. The quantity of makeup permanganate solution depends upon the quantity of olefins in the feed stream.

In operation, the resulting aqueous potassium permanganate solution is then introduced into the oxidizer feed pipes by means of conduit 37. Spent aqueous solution containing Mn0 is removed via valve 38 and conduit 39 from oxidizer 15. Likewise valve 40 and conduit 41 serve to remove the spent oxidizing solution from oxidizer 18. By closing valve 42 and opening valve 43 in conduit 44, the streams from oxidizers 15 and 18 are directed into filter tank 45 wherein filter 46 serves to recover MnO from the spent solution prior to passing the remainder through conduit 47 for disposal. By means of conduits 48 and 50 and eductor-mixers 49 and 51, the oxidizing units 15 and -18 are provided with means to recycle and mix the potassium permanganate solution with the hydrocarbon so as to assure complete contacting of the olefin contaminant with the oxidizing solution, thereby assuring essentially complete oxidation of the olefin component in the hydrocarbon stream. This contacting in the eductors is usually in a volume ratio of hydrocarbon to reagent of about 0.5 to 1.0 up to about 10 to 1. Temperature can range from ambient up to about 200 F. Pressure is sufficient to maintain liquid phase. For normal butane treatment, ambient temperature, e.g. F., and about 50 p.s.i.g. is satisfactory.

While the process is preferably carried out as a twostage oxidation treatment, it is within the scope of this invention to carry out the potassium permanganate treatment in a single stage.

Various modifications of this invention can be made, or followed, in view of the foregoing disclosure, without departing from the spirit or scope thereof.

I claim:

A process for the removal of trace olefin contaminants in a liquid n-butane stream containing about 350 p.p.m." olefin contaminants therein which comprises saturating said liquid n-butane stream with Water, treating the resulting water saturated n-butane stream with an aqueous solution of potassium permanganate containing from 2 to 5 weight percent permanganate so as to oxidize the trace olefin contaminants to the corresponding alcohols, separating the resulting alcohols from the n-butane References Cited hy the Examiner UNITED STATES PATENTS 1,110,925 9/1914 Greenstreet 208---295 1,658,171 2/ 1928 McMichael 208270 2,390,720 12/1945 Latchum 260-676 2,473,224 6/ 1949 Schneider et a1 260-676 3,129,253 4/1964 Odioso et -al 260--676 3,154,586 10/1964 Bander et a1. 260-641 ALPHONSO D. SULLIVAN, Primary Examiner. 

